Development of a Foot-and-Mouth Disease Virus Serotype A Empty Capsid Subunit Vaccine Using Silkworm (Bombyx mori) Pupae

Foot-and-mouth disease (FMD) is a highly contagious disease of cloven-hoofed animals that inflicts severe economic losses in the livestock industry. In 2009, FMDV serotype A caused outbreaks of FMD in cattle in China. Although an inactivated virus vaccine has proven effective to control FMD, its use may lead to new disease outbreaks due to a possible incomplete inactivation of the virus during the manufacturing process. Here, we expressed the P1-2A and the 3C coding regions of a serotype A FMDV field isolate in silkworm pupae (Bombyx mori) and evaluated the immunogenicity of the expression products. Four of five cattle vaccinated with these proteins developed high titers of FMDV-specific antibody and were completely protected against virulent homologous virus challenge with 10,000 50% bovine infectious doses (BID(50)). Furthermore, the 50% bovine protective dose (PD(50)) test was performed to assess the bovine potency of the empty capsid subunit vaccine and was shown to achieve 4.33 PD(50) per dose. These data provide evidence that silkworm pupae can be used to express immunogenic FMDV proteins. This strategy might be used to develop a new generation of empty capsid subunit vaccines against a variety of diseases.